The field of the invention is generally that of solar energy heating apparatus or solar energy power plants, a great many different forms of which have been developed in the prior art. For example, there have been solar ovens or solar cookers developed where large lenses or focusing mirrors are employed in a manner analagous to the widely-experienced practice of youngsters in using a conventional reading type of magnifying lens for focusing sunlight onto a very small concentrated spot on a material having a low ignition temperature (such as paper or the like) and either burning a hole in the paper or actually setting it on fire. In such prior art solar cookers or ovens, such concentrated heat is focused on a food object, or into a closed region containing a food object, so that the food object will be heated and all of the entering focused heat will be captured and retained, thus having an oven-like cooking effect on the food object. There have been other prior art solar energy power plants which have employed a similar focusing principle for attempting to produce in a small area a very high temperature from banks of lenses and/or focusing mirrors for heating use or for use as input to a heat engine. There have also been large surface area solar energy receptor panels (often roof-mounted, usually colored as nearly black as possible for maximum receptivity, for imparting heat at a relatively low level to a considerable volume of circulatable liquid which can then be piped through a building for providing interior heating, primarily by radiation into the interior space areas which are desired to be heated. However, there have also been certain moving solar energy focusing systems devised in the past, but virtually all of such prior art systems have had disadvantages of one type or another. The least disadvantages of said prior art systems has comprised certain of the solar cookers or solar ovens which have worked reasonably well, although they have been somewhat delicate and, in certain cases, somewhat expensive and in virtually all cases, have been subject to meteorlogical variations in the available solar energy for use in such solar energy cookers.
Probably the second least disadvantaged of the above-mentioned prior art types of solar energy systems comprises the large area flat panel solar energy collectors used for heating circulatable liquids to a relatively low temperature for circulation within a building for space heating purposes and the like. Certain of said systems have worked reasonably well, although being somewhat limited by the relatively large capital cost of the initial system and the cost of installation thereof, plus also being subject to the vagaries of the weather. The least efficient of the prior art solar energy systems mentioned above has been the type of system intended to comprise a power plant having a useful mechanical power output or electrical power output because of the relatively low temperature of any solar-energy-heated working medium fed to a heat engine as input energy, which always greatly decreases the efficiency of such a system and the relative capital cost per unit of output power produced by such a system. Additionally, the types of such prior art solar energy power plant systems which attempted to increase the input temperature of the working medium by laying great stress on the initial focusing of very large quantities of sunlight onto a very small heat transfer area associated with the working medium, have had the major disadvantage of the very great cost involved for the kind of lens and/or focusing mirror means required for this type of system, plus the great fragility of a relatively large system employing either few very large solar energy collectors and focusers or large banks of smaller ones.
It is obvious that any solar energy conversion apparatus which would not require such excessively large and expensive optical means for transferring solar energy into a working medium in a manner such as to raise the temperature of the working medium to a relatively high level for greater efficiency of operation of a power plant fed thereby would be a highly advantageous apparatus or system and it is precisely desirable and advantageous type of solar energy conversion apparatus that is provided by, and in, the present invention, which has advantages virtually completely overcoming a good many of the prior art problems, disadvantages, and limitations, such as certain of those mentioned hereinbefore, and all of which advantages flow from and occur by reason of the specific features of the invention pointed out hereinafter.